Snap-action switches generally and precision snap-action switches in particular are produced and distributed by many manufacturers with internationally standardized dimensions so that the snap-action mechanism of these switches have had the same dimensions for many years. Constructional and characteristical features of such switches are described e.g. in the Catalogue No. Z-007 of OMRON Tateisi Electronics Co., Japan issued on May, 1970, or in any "Basic switches Catalogue" of Honeywell, U.S. The actuated element of the snap-action mechanism is expanded in the ground state by the arched spring element laying on both sides of the inner actuated element. The opposite end of the spring element is supported in a tilting bearing while the free end of the actuated element is fixed on the case of the switch. On the common part of the actuated element and the spring element a moving contact, generally a double contact, is arranged between a fixed contact which is normally closed (N.C.) and a fixed contact which is normally open (N.O.). The actuator, having an operating axis perpendicular to the longitudinal axis of the snap-action switch, is provided with a convex, practically point-shaped actuating surface. The actuator bends the actuated element near the common axis of the tilting bearing of the spring element during the operation and after reaching the dead-point position the actuated element snaps over and the moving contact snaps into engagement with the fixed contact N.O. during existance application of the operating force. After relief of the operating force, the snap-action mechanism snaps back from the operating position to its original position. Another type of snap-action switches is known wherein the middle lever of the snap-action mechanism is formed as an arched spring element while both the outer actuated elements are bound in the zone of the moving contact and in the contacting zone of the actuator.
One of the most difficult things to achieve with the known snap-action switches is a reduced contact movement and force differential without reduction of contact separation. Because of reduction of the contact separation the movement differential decreases, so that the force differential and the operating force decrease. Reduction of contact separation has a disadvantageous reaction on the power characteristics, since decrease of the operating force goes with the decrease of the contact force which increases the possibility of the burning of the contacts. Burning of the contacts has a negative effect on the power characteristics of the snap-action switch. Switches of the prior art have the disadvantage that, upon use of the switch in D.C. circuits and with a voltage higher than the arc-striking voltage, the contact of the negative pole tapers on the occasion of the arc-striking so that the small contact separation disappears after relatively few operating cycles and the switch becomes unable to switch through.
Because of the aforementioned drawbacks standard specifications limit the reduction of the contact separation, for that very reason it is impossible to attain more advantageous movement differentials and force differentials with the snap-action mechanism of the known switches than with a snap-action mechanism having a contact separation e.g. of 0.5 mm.